The invention concerns a self-propelled operating apparatus for the regeneration, in place, of road pavement made of a bituminous mix, utilizing pavement heating, a radio-frequency microwave generator couple with at least an illuminator device of the slotted wave-guide type, which is able to radiate and distribute toward the ground, the produced energy.
Through one passage only of the apparatus it is feasible to heat the road paving or carpet along the whole width of a lane up to 4 to 4.5 m, to scarify the layer for the whole desired thickness, to regenerate the removed material with optional additions of bitumen and/or filler, to lay off on the ground and to effect a first compaction of the regenerated material, so eliminating the need of transporting materials to the discharge point and of conveying the new mix.
The feeding velocity of the apparatus during the operational phase is foreseen to be up to 4 m per minute.
According to the invention, all the elements and members composing the apparatus are dimensioned in such a way that the whole work will be effected without any discontinuity. In other words, the amount of bituminous mix heated, ripped, collected, raised and entering a homogenizing-mixing device in a certain interval of time, determined as a function of the feeding speed, is such that in the same interval of time the same amount of bituminous mix, with optional additions of bitumen and/or filler will be treated by said homogenizing-mixing device and then discharged, distributed and compacted, so achieving the whole and total regeneration of the road carpet.
By means of the employment of heating sets according to the invention it is feasible to control the depth of the heated layer, so that, without modifying the temperature and the feeding speed of the apparatus, such thickness will be larger than the thickness of the layer that one wants actually to scarify, in order to subject it to the mixing and homogenizing treatment.
The heating of the deeper layer appears to be advantageous, since it allows the elimination of possible crackings present in the layer. This result cannot be achieved through the employment of conventional heat sources, whose action is limited to a thickness of a few centimeters, generally 3 to 5 cm.
According to a further feature of the invention, it is foreseen that a scraping blade and a chute can be lifted, so that the material, heated, scarified by means of rippers and removed by collecting and distributing screw feeders, may be directly compacted by a finishing machine, thus avoiding the passage through the device of the homogenizing and mixing treatment, with or without the addition of filler and/or binder, whenever it is deemed to be unnecessary.
The bitumen, out of the contact with the air and protected from the light, keeps, practically for an unlimited period of time, its own physical-chemical and rheological characteristics.
The bituminous mix for road superstructures, substantially composed of a hot mixture of aggregate lithoid materials and bitumen, follows completely the abovementioned law, keeping substantially unchanged the rheological characteristics which it has acquired at the moment of its preparation and laying off.
The end of the useful life of the road pavings of this type takes place usually owing to the fatigue failure of the layers which are bound with the bitumen. Breaks are formed which cross the layers, so that water and dust can penetrate into said breaks thus creating diaphragms which make the deterioration process an irreversible one.
The widening and extending of the breaks involve ratchiness formation, holes and break-through actions until the demolition and the remaking of the paving layers cannot be delayed any more.
the residues of the demolition of a paving, if they are heated with proper care upto the temperature of the original paving preparation (150.degree.-180.degree. C.) and mixed again, give rise to bituminous mixes whose features are completely similar to the original ones, and give rise to pavings, whose behaviour and strength are almost equal to those of the first installation.
To date, the regeneration of said materials in placehas never been advantageously achieved on an operational scale owing to the difficulty of providing heating systems suitable to prevent the alteration and deterioration of the characteristics of the bituminous binder.
It is known, indeed, that the bitumen loses completely or partially its binding qualities if it is heated to temperatures exceeding 200.degree. C. approximately. Even a heating effected within said temperature limits, if it takes place in the presence of air, implies oxidation phenomena which alter its essential properties.
With systems now known, since the bitumen and the aggregate mateials are bad conductors, in order to correctly heat the heap of fragments, a prolonged exposition is needed to low-temperature heat-sources, in a conventional way, which makes any apparatus for the regeneration of the materials in place and their reuse for the remaking of the damaged paving disadvantageous .
The above explains the reason why until today, in the case of maintenance interventions upon a roadway, particularly in the cases which do not concern only the "cortical" portion, that is the worn layer only, the method is still accepted of the demolition of the bituminous paving, for instance by means of a tearing action, followed by the removal and the transport of the demolished material to a dumping place, and the re-building of the paving with a new bituminous mix, with all the related inconveniences.